Common Latin legal phrases show up in pleadings, oral arguments, and judicial opinions because they pin legal concepts to fixed definitions that ordinary English words no longer carry. Below is a working glossary of the terms you’re most likely to encounter, organized by where they usually appear.
Terms You’ll Hear in Civil Litigation
Pro se means “for oneself” and describes a person who represents themselves in court without an attorney. Federal law guarantees the right to self-representation in all federal courts, and every state extends the same right. Going pro se doesn’t loosen any rules. You still have to meet every filing deadline, follow every procedural requirement, and present evidence correctly. Judges will not coach you through the process. Courts sometimes appoint standby counsel to help with procedural mechanics, but the pro se litigant remains responsible for the case.
Prima facie translates roughly to “at first sight.” Before a civil case moves forward, the plaintiff must present enough evidence on every element of the claim that a reasonable jury could rule in their favor. If the evidence falls short at this early stage, the judge can dismiss the case outright. The concept works as a gatekeeping mechanism: your claim has to show real substance before the court invests time and resources in a full trial.
A subpoena is a formal court order compelling someone outside the lawsuit to appear or hand over records.1United States Courts. AO 88A Subpoena to Testify at a Deposition in a Civil Action Ignoring one is not an option. A person who refuses to comply faces contempt of court, and federal law authorizes penalties of up to $1,000 and six months of imprisonment for willful disobedience of a court order.
A guardian ad litem is appointed when a lawsuit involves a child or an adult who lacks the mental capacity to make legal decisions. This person’s sole job is to represent the interests of someone who cannot speak for themselves in the proceedings. A guardian ad litem is not a parent, family member, or personal attorney. They serve as the court’s eyes and ears, investigating the situation and making recommendations that protect the vulnerable party rather than advancing any side’s litigation strategy.
Res ipsa loquitur means “the thing speaks for itself.” It’s a tort doctrine that lets a plaintiff establish negligence through circumstantial evidence alone when the facts make negligence the only reasonable explanation. To use it, a plaintiff must show three things: the accident is the kind that does not ordinarily happen without someone being negligent, the thing that caused the injury was entirely under the defendant’s control, and the plaintiff did nothing to contribute to the harm.2Legal Information Institute. Res Ipsa Loquitur A surgical sponge left inside a patient is the classic example. The patient was unconscious, the surgical team had exclusive control, and sponges do not end up inside people absent negligence.
Terms Used in Criminal Cases
Actus reus is the physical act of committing a crime. It can be an affirmative action, like taking someone’s property, or a failure to act when you had a legal duty to do so, like a lifeguard who watches a swimmer drown without intervening. The key word is “voluntary.” Reflexive or unconscious movements do not count. If your body moved involuntarily and caused harm, the actus reus element is missing and there is no crime.
Mens rea is the guilty mental state. Prosecutors must show what was going on in the defendant’s mind at the time of the act, which is what separates a tragic accident from a punishable offense. Criminal statutes define different levels of mental culpability, ranging from acting purposely or knowingly at the top to recklessly or negligently at the bottom. Which level the government must prove depends on the specific crime charged, and that distinction has enormous consequences for sentencing.
Corpus delicti means “body of the crime.” The doctrine prevents the government from convicting someone based on nothing more than a confession. Before a prosecution can move forward, independent evidence must establish that a crime actually took place.3Legal Information Institute. Corpus Delicti If a person walks into a police station and confesses to a murder but no victim, no body, and no evidence of any killing exists, that confession alone cannot sustain a conviction. False confessions happen more often than most people realize, and the rule exists as a safeguard against them.
Habeas corpus translates to “you shall have the body.” A person who has been detained or imprisoned can use a writ of habeas corpus to challenge the legality of that confinement, forcing the government to justify why it is holding someone in custody.4Constitution Annotated. Suspension Clause and Writ of Habeas Corpus The writ is not limited to criminal defendants. Anyone in government custody, including immigration detainees and people committed to psychiatric institutions, can petition for habeas review.
Nolo contendere, “I do not wish to contest,” is a plea whose criminal consequences are identical to a guilty plea: the court can impose the same sentence, fines, and conditions. The difference matters later. A guilty plea can be used as evidence against you in a later civil lawsuit arising from the same conduct, but a nolo contendere plea generally cannot.5Legal Information Institute. Federal Rules of Criminal Procedure Rule 11 – Pleas That distinction makes the nolo plea attractive for defendants who want to resolve criminal charges without handing future civil plaintiffs a ready-made admission. Not every court is required to accept one. In federal court, the judge must weigh the parties’ views and the public interest before agreeing to the plea.
Voir dire is the process of questioning prospective jurors to identify bias before trial begins. The phrase actually comes from Old French rather than Latin, but it sits so squarely alongside the Latin terms in legal usage that it belongs in any working list. During voir dire, the court asks whether jurors know any of the parties, have personal experience with the type of case, or hold views that would prevent them from being impartial.6United States Courts. Juror Selection Process Attorneys can then challenge jurors either for cause, meaning they articulate a specific reason, or through a limited number of peremptory challenges that require no stated justification.
Terms About Court Authority and Procedure
Stare decisis, “to stand by things decided,” is the reason court decisions have lasting power. It requires judges to follow the legal principles established in earlier rulings by higher courts within the same jurisdiction.7Constitution Annotated. Stare Decisis Doctrine Generally Without it, the law would change unpredictably from case to case. The doctrine is not absolute. Courts can depart from prior rulings when they identify strong justifications for doing so, which is how landmark decisions occasionally overrule earlier ones.
A writ of certiorari is what a party files when they want the Supreme Court to hear their case after losing in a lower appellate court. The Court is under no obligation to accept. Its own rules state that review on certiorari “is not a matter of right, but of judicial discretion,” granted only for “compelling reasons.”8Office of the Law Revision Counsel. 28 USC App – Rules of the Supreme Court of the United States – Section: Rule 10 The Court typically agrees to hear cases that involve conflicting rulings among lower courts or significant questions of federal law. Out of thousands of petitions filed each year, the Court accepts fewer than 100.
Res judicata, “a matter judged,” bars the same parties from relitigating the same claim after a final judgment. This applies whether you won or lost. A plaintiff who prevailed cannot file a second lawsuit seeking additional recovery on the same cause of action, and a losing plaintiff cannot take another shot at it. The doctrine preserves the finality of court decisions.
An amicus curiae brief, “friend of the court,” is a filing from someone who is not a party to the case but believes the outcome will affect interests beyond the two sides. These come from organizations, government agencies, or individuals. The Supreme Court’s own rules make clear that a helpful amicus brief brings relevant information the parties themselves have not raised, while one that simply echoes an existing argument “burdens the Court” and is discouraged.9Legal Information Institute. Supreme Court Rule 37 – Brief for an Amicus Curiae In high-profile constitutional cases, dozens of amicus briefs may arrive from every direction.
A court acts sua sponte, “of one’s own accord,” when it takes action on its own initiative without either party requesting it. A judge might dismiss a case sua sponte for lack of jurisdiction, even when both sides want the case to proceed, because courts have an independent obligation to ensure they have authority over the dispute before them. Judges can also raise procedural deficiencies sua sponte, such as missed deadlines or failure to follow court rules.
An ex parte proceeding or communication involves only one side of a case. Judicial ethics rules generally prohibit ex parte contact with judges, because fairness requires both sides to have an equal opportunity to be heard.10Central District of Illinois. Guidelines for Communicating with the Court The exception is emergency situations where waiting for the other side could cause irreparable harm. Courts can issue temporary ex parte orders in genuine emergencies, such as domestic violence situations or imminent destruction of property, but these orders are short-lived. The court quickly schedules a full hearing where both parties can present their case.
De novo means “anew” or “from the beginning.” When an appellate court conducts a de novo review, it reexamines the legal question from scratch without giving any deference to the lower court’s conclusion.11Legal Information Institute. De Novo This standard applies most commonly to pure questions of law, where the appellate court is in just as good a position to interpret a statute or constitutional provision as the trial judge was. Factual findings usually receive more deference on appeal, because the trial court had the advantage of seeing witnesses testify in person.
In camera means “in chambers.” An in camera review happens when a judge examines evidence privately, outside the presence of the parties, the jury, and the public. Judges use this procedure most often when one side claims that certain documents are protected by attorney-client privilege or another legal protection.12Legal Information Institute. In Camera Rather than forcing disclosure of potentially privileged material just so the other side can argue about it, the judge reviews the documents alone and decides whether the privilege applies.
Forum non conveniens, “inconvenient forum,” is the doctrine a defendant invokes to ask the court to dismiss a case that has been filed in the wrong location. The court weighs a range of factors, including where the evidence is located, where the witnesses live, and whether another court with jurisdiction would be more practical for everyone involved.13Legal Information Institute. Forum Non Conveniens The defendant must also show that an adequate alternative court exists and can actually provide a remedy. Courts give significant weight to the plaintiff’s choice of forum, so these motions succeed only when the balance tips heavily toward the defendant.
Terms in Contract and Commercial Dealings
Caveat emptor, “let the buyer beware,” historically placed the burden on purchasers to inspect goods before buying them. A buyer who failed to examine what they were purchasing could not later complain about defects that a reasonable inspection would have caught. Modern consumer protection laws have significantly eroded caveat emptor in many contexts, particularly for new products and residential real estate, but the concept still surfaces in sales of used goods, auction purchases, and commercial transactions between sophisticated parties.
Quid pro quo, “something for something,” describes the mutual exchange at the heart of a binding contract. Each party must provide something of value, whether that is money, services, a promise, or giving up a legal right. Without this exchange, you have a gift or a bare promise, neither of which is enforceable as a contract. Outside of contract law, the phrase appears frequently in employment discrimination cases, where quid pro quo harassment involves conditioning a workplace benefit on unwelcome conduct.
Bona fide means “in good faith” and describes actions taken honestly and without intent to deceive. Nearly every contract in the United States carries an implied duty of good faith and fair dealing, which means neither side can use the agreement’s terms as a weapon to undermine the other party’s reasonable expectations. A landlord who technically complies with a lease but deliberately makes conditions unlivable to force a tenant out violates this implied duty even if no specific lease term was broken.
Quantum meruit, “as much as is deserved,” lets a court award compensation when no valid contract exists but one party has performed work that benefited another. The award is based on the reasonable value of the services provided, not on any agreed-upon price, because no enforceable agreement existed in the first place.14Legal Information Institute. Quantum Meruit This remedy frequently comes into play when a contract turns out to be void for a technical reason or when work was performed based on an oral understanding that never became a formal agreement.
Pro bono publico, commonly shortened to pro bono, means “for the public good” and refers to legal services provided free of charge to people who cannot afford representation. The legal profession’s national ethics framework encourages every lawyer to contribute at least 50 hours of pro bono work per year, with priority given to serving people of limited means. No state currently makes pro bono work mandatory, but many courts and bar associations track participation and publicly recognize attorneys who meet or exceed the aspirational target.
Terms in Property Law
Lis pendens, “pending litigation,” is a public notice recorded in a county’s property records that warns anyone interested in a piece of real estate that a lawsuit affecting the property’s title is underway. The filing does not technically prevent a sale, but it effectively freezes most transactions because title insurance companies will not insure property with a lis pendens on it, and few buyers or lenders will proceed without title insurance. Anyone who purchases the property after the notice is recorded takes it subject to the outcome of the lawsuit, meaning they could lose the property entirely if the plaintiff prevails. Lis pendens filings most commonly appear in foreclosure actions, boundary disputes, and divorce proceedings where one spouse claims an interest in property titled to the other.